1. Field of the Invention
The present invention generally relates to digital data processing systems and more particularly relates to multiple digital data processing systems, which may be reconfigured.
2. Description of the Prior Art
The earliest digital data processing systems tended to employ fixed configurations with regard to processing resources. The memory spaces were of fixed dimensions, the input.backslash.output channels were hardwired and/or hard coded, and specific peripheral equipments were identified to the operating software with fixed characteristics.
As data processing systems grew in complexity and capability, resources were given more relative and logical, rather than fixed and specific characteristics. A major step was providing input/output subchannels with the capability of dynamic allocation as taught in U.S. Pat. No. 4,437,157, issued to Witalka et al. Logical file designations for peripheral devices is suggested by U.S. Pat. No. 5,014,197, issued to Wolf. Similarly, U.S. Pat. No. 4,979,107, issued to Advani et al., suggests logical assignment of peripheral subsystem operating parameters.
The capability to reconfigure has been used in a number of systems applications. U.S. Pat. No. 4,070,704, issued to Calle et al., provides a boot strap program with the capability to change the initial load peripheral device upon determination of a failure in the primary loading channel. Perhaps the most often stated purpose for reconfiguration is to provide some degree of fault tolerance. U.S. Pat. No. 4,891,810, issued to de Corlieu et al., and U.S. Pat. No. 4,868,818, issued to Madan et al., suggest system reconfiguration for that reason. A related but not identical purpose is found in U.S. Pat. No. 4,888,771, issued to Benignus et al., which reconfigures for testing and maintenance.
The capability to reconfigure a data processing system can support centralized system control as found in U.S. Pat. No. 4,995,035, issued to Cole, et al. A current approach is through the assignment of logical names for resources as found in U.S. Pat. No. 4,245,306, issued to Besemer et al. and U.S. Pat. No. 5,125,081, issued to Chiba. An extension of the capability to identify resources by logical names is a virtual system in which the user need not be concerned with physical device limitations, such as suggested in U.S. Pat. No. 5,113,522, issued to Dinwiddie, Jr. et al.
Though the prior art does show some of the rudiments of system reconfiguration, the focus tends to be upon a single integrated system with resources being added or deleted. A primary advantage in reconfiguration of resources is when managing multiple systems to accommodate resources which may be more globally shared.